The present invention relates to sunscreen formulations. In particular, the invention relates to a sunscreen formulation containing avobenzone.
Avobenzone is a wide spectrum UVA sunscreen which has recently been approved by the Food and Drug Administration ("FDA") for use in the United States. Due to its wide spectrum it is presently the most efficient UVA sunscreen on the market. In addition to UVA protection, a sunscreen must also provide UVB protection. In that respect, octocrylene and octyl-methoxycinnamate are both known to be efficient UVB sunscreens. Accordingly, a sunscreen formulation containing avobenzone as a UVA blocker requires a UVB blocker, such as octocrylene or octyl-methoxycinnamate in order to provide protection against both UVA and UVB.
The FDA limits the amount of octocrylene in a sunscreen to no more than ten percent (10%) by weight. Similarly, the FDA limits the amount of octyl-methoxycinnamate which can be used in a sunscreen to seven and one-half percent (7.5%) by weight. Due to these limitations on the amount of either octocrylene or octyl-methoxycinnamate which the FDA permits, it is not possible to provide a sunscreen containing avobenzone and either octocrylene or octyl-methoxycinnamate which would provide a formulation having a sun protection factor ("SPF") of SPF 30. Accordingly, it is known to combine multiple UVB blocks such as octocrylene and octyl-methoxycinnamate together in a formulation which is then able to provide an overall formulation having an SPF 30.
Notwithstanding the wide spectrum UVA protection provided by avobenzone, a known problem with avobenzone is that it is photodegradable. In particular, exposure of avobenzone to light causes a degradation of its sunscreen protection capabilities. It has heretofore been found, as described in U.S. Pat. No. 5,587,150 entitled PHOTOSTABLE COSMETIC SCREENING COMPOSITION CONTAINING A UV-A SCREENING AGENT AND AN ALKYL BETA., BETA-DIPHENYLACRYLATE OR ALPHA-CYANO BETA., BETA-DIPHENYLACRYLATE which issued to A. Deflandre, et als. on Dec. 24, 1996 that by combining octocrylene with avobenzone, the avobenzone will be stabilized and degradation will be substantially eliminated. As set forth above, this combination has the further synergistic effect of adding to the UVB blocking capability of the combination while also boosting the SPF of the combination. Also, U.S. Pat. No. 5,605,680 entitled PHOTOSTABLE COSMETIC COMPOSITION CONTAINING A UV-A SCREEN AND A UV-B SCREEN AND A PROCESS FOR STABILIZING THE UV-A SCREEN WITH THE UV-B SCREEN which issued to A. Deflandre, et als. on Feb. 25, 1997 may be relevant to the present invention.